Odd-even effects and the influence of length and specific positioning of alkoxy side chains on the optical properties of PPE-PPV polymers
Odd-even effects and the influence of length and specific positioning of alkoxy side chains on the optical properties of PPE-PPV polymers
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DOI：
10.1021/cm051437e
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发表时间：
2005-11-29
影响因子：
8.6
通讯作者：
Grumm, UW
中科院分区：
文献类型：
--
作者：
Egbe, DAM;Ulbricht, C;Grumm, UW
这篇文章报道了奇偶效应和烷氧基侧链OR 1 =的特定位置的综合影响。（OCn+H-10（2（n+10）+1））和OR 2 =（OCnH2n+1）（其中n = 6，7，8，9）分别对亚苯基-亚乙炔基和亚苯基-亚乙烯基链段的光学性质的影响，对具有以下一般重复单元的杂化聚合物P（n+10）/n的光学性质的影响：-Ph-C相当于C-Ph-C相当于C-Ph-CH=CH-Ph-CH=CH-。对于聚合物材料，根据烷氧基侧链的奇数和偶数特征，视觉颜色印象在橙子红色（P16/6和P18/8）和黄色（P17/7和P19/9）之间交替变化，其中奇数或偶数与侧链内sp（3）-杂化原子的总数有关。这种侧链相关的效果归因于吸收和发射行为的聚合物的基础上，在本体的物理研究。对于所有四种材料，获得了几乎相同的薄膜吸收光谱;然而，奇数聚合物P16/6（λ（f）= 556 nm）和P18/8（λ（f）= 614 nm）的光致发光相对于它们的偶数对应物（λ（f）= 535 nm）发生了红移。此外，在614 nm处的P18/8最大值可容易地归属于受激准分子发射，如由最大斯托克斯位移（5600 cm（-1））、最大fwhf值（3700 cm（-1））（，）和24%的最低Phi（f）值所证明的。P18/8中的强π-π链间相互作用，由于松散的烷氧基侧链堆积，不仅有利于荧光猝灭，而且还使得在电致发光中产生的正和负极化子的有效的分子间以及分子内重组成为可能，这解释了该聚合物的良好EL性质，而与所使用的溶剂无关。从芳香族溶剂制备的P18/8器件的EL光谱的电压依赖性蓝移高达100 nm。随着电压的增加观察到的这种红色到绿色EL位移归因于聚合物链随着温度的增加而发生的构象变化。
This contribution reports the combined influences of odd-even effects and the specific positioning of alkoxy side chains OR1 = (OCn+H-10(2(n+10)+1)) and OR2 = (OCnH2n+1) (with n = 6, 7, 8, 9) on the phenylene-ethynylene and phenylene- vinylene segments, respectively, on the optical properties of hybrid polymers P(n+10)/n of general repeating unit: -Ph-C equivalent to C-Ph-C equivalent to C-Ph-CH=CH-Ph-CH=CH-. For the polymeric materials, visual color impression varies alternatively between orange red (P16/6 and P18/8) and yellow (P17/7 and P19/9) according to the odd and even features of the alkoxy side chains, where odd or even relates to the total number of sp(3)-hybridized atoms within the side chains. This side chain related effect is ascribed to both absorptive and emissive behaviors of the polymers on the basis of photophysical investigations in the bulk. Almost identical thin film absorption spectra were obtained for all four materials; however, the photoluminescence of the odd polymers, P16/6 (lambda(f) = 556 nm) and P18/8 (lambda(f) = 614 nm), was red-shifted relative to that of their even counterparts (lambda(f) = 535 nm). Further, the P18/8 maximum at 614 nm can be readily assigned to excimer emission, as evidenced by the largest Stokes shift (5600 cm(-1)), largest fwhmf-value (3700 cm(-1))(,) and the lowest Phi(f)-value of 24%. The strong pi-pi interchain interaction in P18/8, due to loose alkoxy side chains packing, does not only favor fluorescence quenching but also enable an effective inter- as well as intra-molecular recombination of the generated positive and negative polarons in electrolurninescence, which explains the good EL properties of this polymer irrespective of the solvent used. A voltage-dependent blue shift of the EL spectra of up to 100 nm was observed for P18/8 devices prepared from aromatic solvents. This red to green EL shift as observed with increasing voltage is assigned to conformational changes of the polymer chains with increasing temperature.